The solubility of Th(IV) hydrous oxide in concentrated NaCl and MgCl[sub 2] solutions

Conference · Fri Sep 01 00:00:00 EDT 1995

OSTI ID:5872439

Sterner, S M; Felmy, A R ^[1]; Novak, C F ^[2]

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1. Battelle, Richland, WA (United States)
2. Sandia National Labs, Albuquerque, NM (United States)

The solubility of Th(IV) hydrous oxide was studied in concentrated 4m and 6m NaCl solutions as well as in MgCl[sub 2] solutions ranging in concentration from 1m to 3m over a broad range of hydrogen ion concentrations. The observed solubilities in all solutions showed the same trend as observed previously of higher solubilities at early equilibration times, usually 7 to 8 days, followed by decreases in solubility with time as the precipitates aged. The trend of decreasing solubility with time was more pronounced in NaCl solutions than in MgCl[sub 2] solutions. The observed ThO[sub 2](am) solubilities in concentrated NaCl solutions (i.e., 4m and 6m) were lower than previously reported solubilities in more dilute NaCl solutions (i.e., < 3M NaCl). The results in MgCl[sub 2] were similar in all solutions regardless of the MgCl[sub 2] concentration. Current thermodynamic models for the solubility of hydrous thorium, oxide in chloride solutions, which primarily describe only aqueous Th[sup 4+]-Cl[sup -] ion-interactions, predicted higher solubilities than observed in 4 and 6m NaCl as well as in all MgCl[sub 2] solutions. An improved aqueous thermodynamic model, which includes ion-interaction parameters for like charged species, is proposed to explain these results.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 5872439
• Report Number(s): SAND-95-2004C; CONF-950946-1; ON: DE95017647
• Resource Relation: Conference: 5. international conference on the chemistry and migration behaviour of actinides and fission products in the geosphere, Saint-Malo (France), 10-15 Sep 1995
• Country of Publication: United States
• Language: English

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